Application of vat dyes to textile fibers



changes the penetration of the dye.

streaky in appearance. 'due to the fact that at certain periods of the Patented May 20, 1930 UNITED STATES PATENT OFFICE- ARTHUR R. THOMPSON, JR, OF CHARLOTTE, NORTH CAROLINA, ASSIGNOR TO ROHM & HAAS COMPANY, A CORPORATION OF DELAWARE APPLICATION OF VAT DYES TO TEXTILE FIBERS 1T0 Drawing.

The so-called vat dyes are customarily applied to fabrics by reducing the dyes with sodium hydrosulphite and then dissolving the reduced dyes in an alkaline solution. Subsequently the dye is reoxidized.

One of the greatest difficulties in-this rocess is to obtain an even penetration o dye and avoid having the resulting product Apparently this is dyeing operation, the sodium hydrosulphite becomes more or less exhausted, either through contact with the air or through the addition of more dye, or through variations of temperature. Additional quantities of hydrosulphite must then be added, which causes violent fluctuations in the hydrosulphite concentration of the dye bath and therefore t is known that the greater the concentration of hydrosulphite, the greater will be the penetration of the dye into the material, but on the other hand, if too much hydrosulphite is used, the dye will be too greatly reduced, which will cause delay in the subsequent reoxidation of the dye on the fiber, which may cause some of the value of the dye to be lost. For this reason, it is important that the hydrosulphite concentration be maintained at a relatively stable value.

I have found that the tendency to streaky and uneven dyeing can be largely overcome by using a sulfoxylate formaldehyde such as sodium sulfoxylate formaldehyde. This material assists in maintaining the dye in the reduced state and permits the use of lower temperatures than have customarily been employed. The use of lower temperatures will somewhat slow up the absorption of the dye, which. will result in obtaining more level shades, but if .desired, a temperature of from 200 to 212 F. may be used. This relatively high temperature may be desirable when dyeing textile materials in dark shades and when penetration is diliicult by the usual method of applying vat colors with the hydrosulphite alone. Even when such higher temperature is used,the addition of the sodium sulfoxylate formaldehyde will maintain the dye in the reduced state for a much longer period the Application filed February 27, 1926. Serial No. 91,250.

than when the hydrosulphite alone is used. I

This process is adapted for use Witlrvarious types of material, but I have found it particularly applicable to the dyeing of rayon which has been found to be difiicult by the usual methods.

The manner in which my process may be carried out will be readily understood from the following illustrative examples. In these examples, the percentages given are all calculated on the weight of the goods.

First ewampZe.-5% of anthrene blue GCD double paste (Colour Index #1113) and 6% of dry caustic soda are mixed with water and heated to about 120 F. Then 4% sodium hydrosulphite, 2 5% sodium sulfoxylate formaldehyde, 4% glue and 2% soluble oil are added and the solution is well agitated to insure thorough mixing. -It is then cooled to room temperature by adding enough cold water to cover the goods. The skeins of rayon are then immersed and worked in the bath for about 40 minutes. After that the skeins are removed and treated in a fresh bath containing 1% sodium perborate at 120 F. for 10 minutes to oxidize the dye. The rayon is then treated in a solution containing 1% of neutral soap on the weight of the rayon at 200 F. for 10 minutes, then rinsed in clear water and carefully dried at a suitable temperature.

Second emampZe.In the same manner as above but at a temperature of 130 a solution is made containing 12% anthrafiavone GC paste (Colour Index #1095), 3% anthrene blue GCD double paste (Colour Index #1113), 7% caustic soda, 6% sodium hydrosnlphite, 2 70 sodium sulfoxylate formaldehyde, 4% glue and 2% of a soluble oil such as Turkey red oil. This mixture is brought up to the correct volume 'for dyeing and is circulated in the usual way through the Franklin dyeing machine at room tempcrature for about 50 minutes. After the removal of the exhausted dye bath from the machine the yarn is oxidized in the same machine by circulating a solution containing 2% of sodium perborate at 120, whereupon the yarn is soaped with 2% of neutral soap at 200 F., washed and dried as usual.

In giving these examples I Wish'it to be clearly understood that I am not limiting myself to exactly these proportions nonto the sequence of operations nor the temperatures and time, since conditions may make it advisable to modify the above percentages; in detail.

\Vhnt I claim is:

A dyeing bath adapted for dyeing lex tile fibers over a temperature range of from room temperature to 212 1. emnprising a vat dye in alkaline solution reduced with sodium hydrosulphite and sodium formaldehyde sul'foxylzite.

ARTHUR R. THOMPSON, JR. 

